Mignini et al. compared dipstick urinalysis to urine culture in 3032 pregnant, asymptomatic patients. When either leukocyte esterase or nitrites were positive on urinalysis, the respective sensitivity and specificity to detect a UTI was 53 and 92%.[45] Since organisms that are not uropathogens also produce leukocyte esterase, it has a greater sensitivity (up to 97%) but lesser specificity (41–86%) than nitrites for UTI detection.[36] When positive nitrites were combined with symptoms of a UTI in a urogynecologic population undergoing cystometry, the sensitivity of a nitrite-positive test to detect a UTI increased from 40 to 89% and the negative predictive value was 96%.[46] The authors concluded that symptom-negative, nitrite-negative patients do not need a urine culture, thus increasing the cost–effectiveness of UTI screening in urogynecologic patients.[46]